This invention relates to laser simulators and has special relation to pulsed light sources. Such sources simulate the reflection from a target which has been illuminated by a laser designator. The laser designator emits a pulsed beam, each pulse being approximately twenty nanoseconds long, and with a fixed pulse repetition frequency, typically ten hertz. A guided missile may be launched in the general direction of such a reflection. The missile's seeker will lock onto the reflection and will guide the missile to the target.
A pulsed laser reflection may be simulated by a laser or by any of a number of other light sources of the appropriate frequency. A pulsed light-emitting-diode (LED) is convenient, and is used both in the prior art and in the present invention.
Simulators are required because the seeker must be tested in the field just before use. The ideal time to perform this test is when the missile is aboard the helicopter which will launch it, just before the helicopter takes off. The simulator should produce enough light to be seen at least ten meters away, so that the simulator's operator may stand that far away and thereby avoid the helicopter's blade. It should be inexpensive and rugged, have long battery life, and give positive assurance that it is working.
This last requirement is important. If the seeker does not track the simulator, the missile must be removed and replaced with a missile whose seeker does track the simulator. If the fault is with the simulator and not with the seeker, this removal and replacement will be useless. The laser designator is designed, however, to use infrared radiation (IR), which is invisible to the human eye. This is done so that enemy soldiers will not know, from their own eyes, that they are targets. Discovering that they are targets (and, more importantly, where the laser designator is) requires sophisticated IR detection equipment, which they may not have. This same design, however, prevents the simulator's operator from simply looking into the simulator to see if it is working.
Prior art devices used high voltage batteries (typically one hundred volts) to produce high power pulses, and thereby attain adequate range. They accordingly drained their batteries quickly. High power meant high cost and high fragility. Further, the self test to see if the simulator was working was limited to assuring that the battery's voltage was still within specifications.